In the configuration of whole music, a part of the most representative climactic subject is called “climax”. In the case of a song, the climax part is a part in which the voice of the singer continues for relatively long time.
On the other hand, the acoustic characteristic of a recorded music is designed so that effect can be exerted when the music is reproduced by relatively large audio equipment. Thus, there is a possibility that sufficiently effective performance may not be achieved in the case where the music is reproduced by, for example, a portable audio device, a small audio device, a vehicle-mounted audio device, or the like.
To solve such a problem, in the portable audio device and the like, the acoustic characteristic is adjusted so that the voice band of the singer of a song, for example, is intensified. However, if such intensification is constantly performed, the voice of the singer will become inconspicuous especially in the climactic climax part and therefore will become unnatural, and that can not be called a good reproduction.
On the other hand, a process has been considered in which the climax part of the music is discriminated, and the acoustic characteristic of a predetermined band is intensified only for the climax period. By performing such a process, since the acoustic characteristic of the climax part, which is originally the performance of the impressive voice, is intensified, the voice will not be unnatural, and therefore it is possible to perform effective reproduction. Conventionally researches have been done with regard to methods for discriminating the climax (see, for example, Patent Document 1). Further, methods for intensifying a specific band of music are known techniques (see, for example, Patent Document 2).
As described above, a process has been considered in which the climax part of the music is discriminated, and the acoustic characteristic of a predetermined band is intensified only for the climax period so as to perform effective reproduction. However, as a method for discriminating the climax, very large equipment is needed according to, for example, the technique disclosed in Patent Document 1, and therefore it is not easy to implement such method in the portable audio device or the like. Further, in the technique disclosed in Patent Document 1, the climax part is discriminated from the whole music, and therefore it is necessary to previously perform a discrimination process, so that such technique can not be applied to the music that is being currently played.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-233965    Patent Document 2: Japanese Unexamined Patent Application Publication No. Hei7-106878